Catalytic converters treat exhaust gas streams of combustion engines to convert, trap, and/or adsorb undesirable components in order to meet stringent emissions standards. Components used in catalytic converters include, but are not limited to platinum group metals (PGM), base metals (BM), oxygen storage components (OSC), and/or molecular sieves—such as zeolites. Catalytic converters are designed to meet the needs of specific applications such as exhaust streams of diesel engines (e.g., Diesel Oxidation Catalysts (DOCs), Selective Catalytic Reduction (SCR) catalysts, and Catalyzed Soot Filters (CSF)) and of gasoline engines (Three-Way Conversion (TWC) catalysts). Zoned and/or layered catalysts are further designed used to achieve specific chemistries at specific locations.
Multi-zoned catalysts and traps are disclosed in U.S. Pat. No. 7,189,376 (Kumar). An overcoat layer to provide poison-resistant catalysts is provided in U.S. Pat. No. 7,749,472 (Chen).
There is a continuing need in the art for zoned catalytic articles that provide excellent catalytic activity, component trapping, and/or adsorbing properties.